Known devices comprise plates, and pins which are intended to be held in place through said plates by means of a locking bushing. The plates extend longitudinally in order to be able to be adjusted along the bone elements situated in the continuation of each other, and they have at least two tapped orifices which are respectively situated opposite the two bone elements. The tapped orifices obviously extend all the way through the plates.
As regards the locking bushings, they comprise a screwable part, and a drive part on top of the screwable part. Moreover, the two parts are separated from each other by a groove formed on the locking bushing. The screwable part has a free edge, and it has the general shape of a frustum, its diameter decreasing from the aforementioned groove toward the free edge. In addition, it has axial slits thus defining notches. During assembly, the plate is adjusted along the bone elements, whereas the pins are respectively anchored in these bone elements through the tapped orifices. After the anchoring, the pins have a residual free part which protrudes from the plate and on which the locking bushings will be engaged. The internal diameter of these bushings corresponds, allowing for functional clearance, to the external diameter of the pins, which makes it possible to guide them in translation. The screwable part is then brought to the area of the tapped orifice, and the bushing is engaged in rotation by means of the drive part arranged on top of it. When the screwable part engages with the threads of the tapped orifice, account being taken of its general frustoconical shape, the notches defined by the slits tend to deform concentrically, thus forming jaws which progressively clamp the pin. At a final stage of the driving in rotation of the screwable part, the pin remains in a fixed position with respect to the plate, the screwable part of the bushing being engaged with force between the walls of the tapped orifice of the plate and the pin. Obviously, such a procedure is undertaken for both pins, so as to hold the two bone elements in a fixed position relative to each other.
Thereafter, using cutting pliers engaged at right angles to the aforementioned groove, the bushing and the protruding pin part are both shorn off. In this way, the face of the plate opposite the bone elements is freed of the protruding elements, that is to say the drive part of the bushing and the free part of the pin, whereas the pin part anchored in the bone elements is rigidly connected to the plate by virtue of the locking bushing that clamps it.
Reference may be made to the document FR 2 905 589, which describes an osteosynthesis device of this kind.
These devices are presently in use and, although they permit rapid intervention and a good hold of the bone elements for a period of time sufficient for their consolidation, as compared to the previous generations of osteosynthesis devices, there is still a need for devices that are more effective and less expensive to use.
Thus, a problem which arises, and which is addressed by the present invention, is to make available a device that is more economical, easier to use and provides a high degree of reliability after it has been fitted.